Lymphatic SystemLymphatic System

• Why do we study the lymphatic system?

• Why is it important to us?

Seeing your immune systemSeeing your immune system• When you get a cut…all sorts of bacteria and

viruses enter your body through the break in the skin.

• When a mosquito bites you, you get a red, itchy bump.

• You inhale thousands of germs (bacteria and viruses) that are floating in the air.

• Each day you eat hundreds of germs

• Allergies

• Organ Transplants

Functions of the Lymphatic SystemFunctions of the Lymphatic SystemNot only….

• helps defend the body against disease- causing agents

But also….

• absorbs fats

• transports excess fluid to the bloodstream

What makes up the Lymphatic What makes up the Lymphatic System?System?

First Line of Defense:• Skin

– Primary boundary between germs and your body– Secretes antibacterial substances

• Nose, Mouth, and Eyes– Tears contain an enzyme that breaks down the cell

wall of many bacteria– Saliva is antibacterial– Nasal passages and lungs are coated in mucus, so

many germs not killed immediately are trapped in the mucus and swallowed.

And then also the…..

• Lymph System • Thymus• Spleen• Malt

– Peyer’s patches– Tonsils– appendix

• Bone Marrow• White Blood Cells• Antibodies

Lymph SystemLymph System

• Closely resembles the Circulatory System

• One way system

• Composed of:

Lymph Capillaries

Lymph Vessels

Lymph Nodes

Lymphatic trunks and ducts

• Lymph is simply tissue fluid that has entered the lymphatic system

• Lymph formation prevents the accumulation of excess tissue fluid, or edema

But first….What is lymph?But first….What is lymph?

• A clearish liquid that bathes the cells with water and nutrients; basically, blood plasma – the liquid that makes up the blood minus the red and white cells.

• Blood transfers food, water, hormones, and oxygen to the lymph through the capillary walls, and lymph carries it to the cells.

• The cells produce proteins and waste products and the lymph absorbs these products and carries them away.

LYMPHLYMPH

Why is this a problem?Why is this a problem?

• Proteins, bacteria and virus are prevented from entering blood capillaries but easily enter the lymph capillaries

Bacteria and viruses can then use the lymphatic system to spread throughout the body

How does lymph move?How does lymph move?

• The lymphatic system does not have a pump like the circulatory system.

• Lymph is transported by:1. Milking action of the skeletal muscles

2. Pressure changes during breathing

3. Smooth muscle contraction

• Any interruption in lymph flow can result in edema

Lymphatic System PathwayLymphatic System Pathway

Lymphatic CapillariesLymphatic Capillaries

• Microscopic closed ended tubes that weave between tissue cells, blood capillaries and connective tissue

• Walls are very similar to blood capillaries

The lymphatic capillaries

lead

to lymphatic vessels

Lymphatic VesselsLymphatic Vessels

• Very similar to veins but thinner

• Have valves that prevent backflow

Lymphatic Vessels

lead to

specialized organs called lymph nodes

Lymph NodeLymph Node

• Kidney-bean shaped

• Less than one inch long

• Buried in connective tissue

• 500-600 are located along the lymphatic pathways

• Afferent lymphatic vessels lead to the lymph node

• Efferent vessels lead out of the node

What is the function of What is the function of lymph node?lymph node?

• Filter harmful particles from lymph before returning it to the bloodstream

• When fighting certain infections, the lymph nodes swell with bacteria AND the cells fighting the bacteria….yes, this is why you can feel them when you are sick.

• Swollen lymph nodes are good indication that you have an infection.

• View the lymph nodes at work…..

Immune cells within Immune cells within the lymph nodesthe lymph nodes

• B Lymphocyte

• T Lymphocyte

• MacrophagesNext

B LymphocyteB Lymphocyte

• Originates in red bone marrow

• Produce antibodies• Surface of B Lymph is

covered with receptors that acts as a key to fit specific antigens

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T LymphocyteT Lymphocyte

• Originates in red bone marrow and matures in thymus gland

• These cells kill other cells that are harboring a virus

• 2 types of T lymphocyte

2 Types of T Lymphocytes2 Types of T Lymphocytes

• Helper T cells

• Killer T cells

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Helper T cellsHelper T cells

• Release proteins that stimulate B cells to produce antibodies

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Killer T cellsKiller T cells

• Killer T cells kill antigens on the spot

• Release chemicals that bore into the foreign cells membrane and the contents bursts out of the hole and dies

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MacrophageMacrophage

• White blood cells that continually search for foreign molecules, viruses, or microbes.

• When found, the macrophages engulfs and destroys them.

Do you want to see one…..

Macrophage attacking E.ColiMacrophage attacking E.Coli

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The efferent vessel

leading out of the lymph node

dumps into the

lymphatic vessel

that dumps into the

lymphatic trunk

Lymphatic TrunkLymphatic Trunk

The Trunks1. Lumbar

2. Intestinal

3. Intercostal and bronchomediastinal

4. Subclavian

5. Jugular

The trunks

then join the

collecting ducts

Collecting DuctsCollecting Ducts

Two collecting ducts:

1. Thoracic duct – largest and longest of the two ducts

2. Right lymphatic duct

The collecting ducts

then return

the lymph

back into the blood stream

by way of the

subclavian vein

And on to the other lymphatic organs…..

• Thymus

• Spleen

• MALT – Peyer’s patches– Tonsils– Appendix

• Bone Marrow

Thymus GlandThymus Gland

• Located in the chest between the sternum and the heart

• Soft, bilobed• Larger in children

than in adults

What is the function of What is the function of the thymus gland?the thymus gland?

• Responsible for the Maturation of T-cells– T-cells are produced in the bone marrow but are

transported through the blood to the thymus where they mature

– T-cells are a type of lymphocyte (WBC)

• Produces thymosin– Thymosin is a hormone that encourages

lymphocyte production

SpleenSpleen

• filters blood like the lymph node filters lymph

• filters foreign particles & damaged red blood cells from the blood

• also stores blood that can be released when needed

• You can live without it but makes you more susceptible to infections

Peyer’s PatchesPeyer’s Patches

• found on the walls of intestines

• filter out potentially harmful bacteria that might enter the intestinal tract

TonsilsTonsils

Trap bacteria before entering body through the nose and mouth like armed guards

1. Pharyngeal

2. Palatine

3. Lingual

AppendixAppendix

• not generally credited with significant function

BUT…..

• current evidence tends to involve it in the immunity mechanism

Defense Against InfectionDefense Against Infection

The Immune System

Functions of the Immune SystemFunctions of the Immune System

• Recognize invading microorganisms

• Respond to the organism and try to beat it

• Terminate the response as quickly as the organism is eliminated so as to not damage the host cell

Invadingmicrobes

(pathogens)

External defenses

SkinMucous membranesSecretions

INNATE IMMUNITYRapid responses to a

broad range of microbes

ACQUIRED IMMUNITYSlower responses to

specific microbes

Internal defenses

Phagocytic cells

Inflammatory response

Humoral response(antibodies)Antimicrobial proteins

Natural killer cells Cell-mediated response(cytotoxiclymphocytes)

Two types of defensesTwo types of defenses

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Innate (nonspecific) DefensesInnate (nonspecific) Defenses

• Present from birth and fast acting– Species Resistance– Mechanical Barriers– Chemical Barriers– Fever– Natural Killer (NK) Cells– Inflammation– Phagocytosis

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Species ResistanceSpecies Resistance

• Each species is resistant to certain diseases that may affect other species but is susceptible to diseases other species may resist.

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Mechanical BarriersMechanical Barriers

• Includes the skin & mucous membranes lining passageways of the respiratory, digestive, urinary, & reproductive systems that prevent entrance of some infectious agents.

• Prevention can occur as long as these barriers remain intact.

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•In the trachea, ciliated epithelial cells sweep mucus and any entrapped microbes upward, preventing microbes from entering the lungsReturn

Chemical BarriersChemical Barriers

• enzymes in gastric juice & tears kill some pathogens

• low (acidic) pH in the stomach prevents growth of some bacteria

• high salt concentration in perspiration kills some bacteria

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FeverFever

• viral or bacterial infection stimulates certain lymphocytes to secrete endogenous pyrogen, which temporarily raises body temperature

• higher body temperature & the resulting decrease in blood iron level production by the liver & spleen causes an increase in phagocytic activity that hampers infection

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Natural Killer CellsNatural Killer Cells

• a group of lymphocytes that secrete cytolytic perforins to destroy cells infected by viruses & cancer– Perforins destroy the cell membrane & enhance

inflammation

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InflammationInflammation

• a tissue response to damage, injury, or infection

• produces localized redness, swelling, heat, & pain

• chemicals released by damaged tissues attract white blood cells to the site– in bacterial infection, the resulting mass of white

blood cells, bacterial cells, & damaged tissue may form a thick fluid called pus

Next

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PhagocytosisPhagocytosis

• neutrophils & monocytes are the most active phagocytes in blood– monocytes give rise to macrophages, which

remain in fixed tissues

• phagocytic cells associated with the linings of blood vessels in the bone marrow, liver, spleen, & lymph nodes constitute the mononuclear phagocytic system

• phagocytes remove foreign particles from tissues & body fluids

Next

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Acquired (specific) Immunity Acquired (specific) Immunity

Acquired, not present at birth

and

• slow initial reaction

• Also, referred to as adaptive defenses

• Second line of defense

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Important DefinitionsImportant Definitions• Antigen – any

substance that when introduced to the body is recognized as foreign and activates the immune system

• Antibody – substance produced by the body that can provide immunity against a specific antigen

ImmunityImmunity

• resistance to particular pathogens or to their toxins

“Self”

Molecules that are

part

of the body

“Nonself”

Molecules that are

foreign

to the body

PathogenPathogen

• A disease causing agent.

• Includes bacteria, fungi, viruses, and parasites.

Antibody-Mediated (humoral) Antibody-Mediated (humoral) ImmunityImmunity

• The defense method that uses antibodies, developed from B cells, as the troops to go into battle

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Viral neutralization(blocks binding to host

and opsonization increasesphagocytosis)

Agglutination ofantigen-bearing particles,

such as microbes

Precipitation ofsoluble antigens

Activation of complement systemand pore formation

Binding of antibodies to antigensinactivates antigens by

Bacteria

Solubleantigens

MAC

Complement proteins

Foreign cellPore

Virus

Bacterium

Enhances

Phagocytosis

Macrophage

Cell lysis

Leads to

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Cell-Mediated ImmunityCell-Mediated Immunity

• Immune reaction directed against body cells that have been infected by viruses and bacteria; controlled by T cells.

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First exposure to antigen

Antigens engulfed anddisplayed by dendritic cells

Activate

Humoral immune response Cell-mediated immune response

HelperT cell

Active andmemoryhelperT cells

Gives rise to

Antigens displayedby infected cells

Activate

CytotoxicT cell

Memorycytotoxic

T cells

Gives rise to

Secretedcytokinesactivate

Activecytotoxic

T cells

Defend against infected cells, cancercells, and transplanted tissues

Activate

Gives rise to

Secrete antibodies that defend againstpathogens and toxins in extracellular fluid

Plasmacells

MemoryB cells

B cells

Intact antigens

Classification of ImmunityClassification of Immunity

• Active Immunity

• Passive Immunity

Active ImmunityActive Immunity

• Long-term immunity• Exposure to disease

and survive – naturally acquired active immunity

• Vaccine containing weakened or dead pathogens – artificially acquired active immunity

Passive ImmunityPassive Immunity

• Short-term immunity• Antibodies passed to

fetus or through mother’s milk – Naturally acquired passive immunity

• Anti-serum or gamma globulin – artificially acquired passive immunity

WHAT CAN GO WRONGWHAT CAN GO WRONG

• If the delicate balance of the immune system is disrupted, effects range from minor to often fatal

Autoimmune DiseasesAutoimmune Diseases

• Occurs when your immune system attacks your own “self” cells

• Some bacteria and viruses cause the T cells to attack the body’s own cells.

• Killer T cells start to view other cells in the body as foreign.

Tissue TransplantsTissue Transplants

• The immune system’s ability to distinguish self from non-self limits tissue transplantation

• The immune system can wage war against cells from other individuals

• Transplanted tissues are usually destroyed by the recipient’s immune system

Blood Groups and TransfusionsBlood Groups and Transfusions

• Antigens on red blood cells determine whether a person has type A, B, AB, or O blood

• Antibodies to non-self blood types exist in the body

• Transfusion with incompatible blood leads to destruction of the transfused cells

• Recipient-donor combinations can be fatal or safe

Autoimmune disease leading to damage and inflammation of joints

Rheumatoid Rheumatoid ArthritisArthritis

Other Autoimmune DiseasesOther Autoimmune Diseases

• Systemic lupus erythematosus

• Multiple sclerosis

• Insulin-dependent diabetes

• AIDS

Acquired Immunodeficiency Acquired Immunodeficiency Syndrome (AIDS)Syndrome (AIDS)

• People with AIDS are highly susceptible to opportunistic infections and cancers that take advantage of an immune system in collapse

• Because AIDS arises from loss of helper T cells, it impairs both the humoral and cell-mediated immune responses

• The loss of helper T cells results from infection by the human immunodeficiency virus (HIV)

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1 µm

The spread of HIV is a worldwide problem

The best approach for slowing this spread is education about practices that transmit the virus

AllergiesAllergies

• Allergies are exaggerated (hypersensitive) responses to antigens called allergens

AllergiesAllergies

• In localized allergies such as hay fever, IgE antibodies produced after first exposure to an allergen attach to receptors on mast cells

• The next time the allergen enters the body, it binds to mast cell–associated IgE molecules

• Mast cells release histamine and other mediators that cause vascular changes leading to typical allergy symptoms

Immediate Reaction AllergyImmediate Reaction Allergy

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IgE

Allergen

Granule

Mast cell

Histamine

Anaphylactic ShockAnaphylactic Shock

• An acute allergic response can lead to anaphylactic shock, a life-threatening reaction that can occur within seconds of allergen exposure